Live demonstration: A CMOS sensor platform with 1.2 µm × 2.05 µm electroless-plated 1024 × 1024 microelectrode array for high-sensitivity rapid direct bacteria counting

High-sensitivity rapid direct bacteria counting is an essential key method for point-of-care testing. Counting pathogens (cells, viruses, and bacteria) directly in real time with high sensitivity is useful in maintaining human health and preventing pandemics or bioterrorism. However, conventional counting methods with high sensitivity such as the polymerase chain reaction and cultivation-based biochemical testing are time consuming and require controlled places and well-trained staff. On the other hand, conventional rapid approaches such as immuno-chromatography and ATP bioluminescence schemes are insufficient with respect to sensitivity. As an alternative, electro-chemical sensing approaches using a microelectrode have been intensely investigated because of its high-sensitivity, simplicity, and high-throughput. In this work, a CMOS sensor platform with a bacteria-sized (1.2 μm × 2.05 μm) Au electroless-plated 1024 × 1024 microelectrode array for high-sensitivity rapid direct bacteria counting is demonstrated. For high-sensitivity direct pathogen counting, Au microelectrodes are required to be as small as the target cell. By improving a self-aligned electroless plating technique, the size of microelectrodes on a CMOS sensor chip was successfully reduced to 1.2 μm × 2.05 μm, corresponding to 1/20th of the smallest size reported in literature. Two test chips with 1024 × 1024 and 32 × 32 sensor arrays were fabricated in a 0.6-μm CMOS process and microelectrodes were formed on them using electroless plating. In this demonstration, 2D counting used 32 × 32 sensor arrays with silicone (fig. 1) by CV is introduced.